Study of pico second movie of plasma interaction with optical vortex and particle acceleration

1)利用螺旋移相器产生超短脉冲光学涡旋：通过在玻璃衬底上涂覆一层16步长的SiO*薄膜制成了螺旋移相器。获得了光涡旋(拉盖尔-高斯光束，拓扑荷为1)的亚ps时间分辨率成像：获得了130fs超短钛宝石激光脉冲的倍频。然后利用该紫外光脉冲，利用阴影照相法和干涉仪技术构建了用于测量短寿命等离子体的光学探测系统。利用该探测系统观测了超短脉冲激光的传输和等离子体形成的动力学过程，并研究了它们与激光相位/偏振分布的关系。3)激光产生纵向电场：利用基于液晶光学旋转的偏振分布板，将线偏振光转换为轴对称偏振(径向偏振和方位偏振)，转换效率大于90%。在0.45 mW径向偏振的Nd：YAG激光器焦斑附近观察到10*V/m的纵向电场。因此，用TW级高功率激光器可以实现0.1TV/m的激光加速。4)光涡和径向偏振的粒子加速：0.5-1TW的钛宝石激光脉冲聚焦在固体或气体靶上。测量的电子光谱表明，这些特殊的激光模式可以增强前向加速电子的数量，特别是在高能成分中。5)粒子模拟：新开发了一个粒子模拟程序，用于分析位相/极化分布所引起的影响。这一代码表明，拉盖尔-高斯光束与圆极化相结合时，高能电子的大幅增加。

1) Generation of ultra-short-pulse optical vortex using spiral phase shifter: A spiral phase shifter was fabricated by coating a 16-steppatterned SiO* onto a glass substrate. The phase distribution was in good agreement with that predicted by the computed hologram, and then an optical vortex (Laguerre-Gaussian beam with a topological charge of 1) was successfully obtained.2) Imaging with sub-ps time resolution: A 130-fs ultra-short Ti: sapphire laser pulse was frequency doubled. Then optical probe system was constructed using this UV pulse for measuring short-life plasmas by shadowgraphy and interferometer techniques. The propagation of ultra-short-pulse laser light and the dynamics of plasma formation were observed using this probing system, and their dependence on laser phase/polarization distributions was studied.3) Generation of longitudinal electric field from laser: A linearly polarized light was converted to axially symmetric polarization (radial polarization and azimuthal polarization) with an efficiency greater than 90% using a polarization distributed plate based on an optical rotatory of liquid crystal. A longitudinal electric field of 10*V/m was observed near a focal spot of 0.45-MW radially polarized Nd: YAG laser. Thus 0.1TV/m can be realized using a TW class high power laser.4) Particle acceleration with optical vortex and radial polarization: Ti: sapphire laser pulse of 0.5-1TW was focused onto a solid or gaseous target. The measured electron spectra suggest that these special laser modes can enhance the amount of forward accelerated electrons especially in high energy component.5) Particle simulation: A particle simulation code has been newly developed for the analysis of the effects caused by the phase/polarization distribution. This code showed that the substantial increase of high-energy electrons for combining the Laguerre-Gaussian beam with circular polarization.